Verapamil administration has resulted in occasional life treatening side effects related to its physiological actions. A number of less serious complaints have also been elicited in patients, but these "adverse effects" have rarely either limited the dosage of the drug with could be administered or prevented its continued use. A protocol was developed in order to determine the frequency, significance, and relationship to verapamil administration of these "adverse effects". The incidence of side effects is also being determined for propranolol, a beta adrenergic blocking agent, another cardiac medication used in these same patient groups. Early results indicate that the drug appears to be well tolerated, but a few unsuspected potential side effects may have been uncovered.